石墨烯负载Ti-Ni双金属对MgH_(2)可逆储氢性能的催化改性及机理

Reversible Hydrogen Storage Properties and Mechanisms of MgH_(2) Catalyzed by Bimetal Ti-Ni Supported on Graphene

MgH_(2)具有7.6 wt%的质量储氢密度,丰富的储量以及低廉的价格,是极具应用前景的储氢材料之一。然而,稳定的热力学性质和缓慢的吸放氢反应动力学导致其吸放氢温度偏高,限制了其实际应用。论文研究了非晶TiH_(2)和纳米Ni负载于石墨烯的Ti-Ni@GR催化剂对MgH_(2)的吸放氢性能的改性及其作用机理。结果表明,MgH_(2)-9 wt%Ti-Ni@GR样品在185℃下即开始放氢,较原始MgH_(2)降低约115℃,且放氢产物在室温下就可以进行氢化反应。引入Ti-Ni@GR也显著改善了MgH_(2)的吸放氢动力学性能,在275℃下,15 min内放氢量达6.2 wt%。在100℃下,5 min就能快速吸氢4.8 wt%。经过10次循环后,样品的储氢容量保持率高达97%。机理研究发现,Ti和Ni的活性催化作用及其均匀分散是体系吸放氢性能改善的主要原因。

Magnesium hydride(MgH_(2))is a promising candidate among the hydrogen storage materials due to its high gravimetric capacity(7.6 wt%),earth abundance and low costs.However,the high thermodynamic stability and sluggish de/hydrogenation kinetics of MgH_(2)result in high operation temperatures for hydrogen desorption/absorption,which hinders its practical use.In this paper,the reversible hydrogen absorption/desorption properties and mechanisms of the MgH_(2)modified by amorphous TiH_(2)and nanosized metal Ni loaded on graphene(Ti-Ni@GR)were investigated.Results show that the onset dehydrogenation temperature of MgH_(2)-9 wt%Ti-Ni@GR system was 185℃,which is 115℃lower than that of pristine MgH_(2).The dehydrogenated composite started absorbing hydrogen at room temperature.The kinetics of MgH_(2)was significantly improved after the introduction of Ti-Ni@GR.6.2 wt%of hydrogen was rapidly released within 15 min at 275℃for the system and the dehydrogenated sample absorbed 4.8 wt%H_(2)in 5 min at 100℃.After 10 cycles,the hydrogen capacity retention was determined to be 97%,showing greatly improved cycling stability.The catalytic effects and homogeneous distribution of Ti and Ni are responsible for the improved hydrogen storage properties of the system.